According to The Ubuntu lifecycle and release cadence Ubuntu 16.04 has full support until mid-2021.
Yet when I run:
pip install cryptography
Requirement already satisfied: cryptography in /usr/lib/python2.7/dist-packages (1.2.3)
cryptography 1.2.3 is from March, 2016.
The cryptography package fully supports Python 2.7, and there were dozens of new cryptography versions released since 2016, so why is it impossible to update it?